Latch for single and double throw hook operated disconnect switch



mm M, 1956 Filed April 7, 1954 mmm Jr1 m |m 1tm rrn;r1 .l x 4m M T. A.FJELLSTEDT EJWJU LATCH FOR SINGLE AND DOUBLE THROW HOOK OPERATEDDISCONNECT SWITCH 2 Sheets-Sheet 1 IN VEN TOR.

Thorst a4. Eiel edt B 3244 v ttorny WOW. M, M56 T. A. IFJELLSTEDT W JLATCH FOR SINGLE AND DOUBLE THROW HOOK OPERATED DISCONNECT SWITCH FiledApril '7, 1954 2 Sheets-Sheet 2 fly 5 1 Q 30 '5 e7 20 g 44 INVENTOR.'T/zar 1: v4. Fm, tedt United States Patent LATCH FOR SllNGLE AND DOUBLETHROW HOOK OPERATED DISCONNECT SWITCH Thorsten A. Fjellstedt, Ingleside,Ill., assignor to McGraw Electric Company, Milwaukee, Wis., acorporation of Delaware Application April 7, 1954, Serial No. 421,531

Claims. (Cl. 200-469) This invention relates to electric switches, andmore particularly to a latch usable in combination with a hook stickoperated air-break disconnect switch.

A principal object of this invention is to provide a simplified latchingmechanism which positively secures a movable switch blade in closedcircuit position relative to a fixed terminal but, nevertheless, permitsfacile release thereof by a mechanically advantageous camming actioneven under adverse conditions, such as where the switch is covered withice.

Another object is to arrange the elements of the latch operatingmechanism so that during opening of the switch most of the initialapplied force is expended in prying the blade free of the latch prior toappreciable movement of the switch blade relative to the fixed terminal.

A further object is to provide a latch which is equally adaptable foruse on single or double throw switches and whose performance is largelyunaffected by either lateral or longitudinal misalignment between themovable switch blade and the stationary elements.

These and other objects will become apparent by referring to thespecification and the following drawings in which: r

Fig. 1 is an elevation view of a double throw switch embodying theinvention;

Fig. 2 is a bottom view of the switch shown in Fig. 1;

Fig. 3 is an enlarged elevation view of the invention, partly insection, showing the latch in engaged position; Fig. 4 shows the latchin released position; i t

Fig. 5 is an end elevation view of the invention, partly in section,with parts removed.

Refer now to Fig. 1 where the novel latch assembly is shown adapted tocooperate with a hook operated double throw air-break disconnect switchmounted upon insulators l and in spaced longitudinally relative to theaxis of the switch blade. The center insulator 1a carries a U-shapedhinge member 2 having spaced upstanding legs 3 spanned by a pin 4 uponwhich the swingable tubular blade 5 may be pivoted. Electricalconnection to the hinge member 2 and its integral legs 3 is made throughan adapter 6 which supports the hinge member 2.

On the end insulators 1 are mounted laterally spaced contact fingers orclips 10 for receiving therebetween the free end of blade 5 in very highpressure electrical con tact engagement. To enhance pressure engagementbetween clips 10 and blade 5, flat contact springs 11 are juxtaposed tothe clips 10. One end 12 of each contact "spring 11 bears against a clip10 and the other end 13 of each spring bears against an adapter base 14to which clips ltl are rigidly fastened by riveting or other well knownmeans. Contact springs 11 are activated by retaining pins 16 carried bya tie bar 15 disposed laterally through clips 10 and springs 11.Obviously, when the switch blade 5 is inserted between clips 10, thepins 16 will react against springs 11 in such manner as to developcontact pressure and prevent excessive divergence of the clips 10.

The novel latching assembly for retaining switch blade 5 in contactengagement with clips 10 and for prying the blade to open circuitposition is shown in Fig. 1 displaced from the contact clips 10 in adirection along the longitudinal axis of blade 5 as indicated generallyby the reference numeral 20.

Latch assembly 20 comprises a support member having two laterally spacedlegs 21 integral with a bottom portion 22 which is fastened to adapterbase 14 by means of bolts 23. A pivot pin 24 bridges the legs 21 and hasits ends peened to prevent lateral removal therefrom. A latch 25 isjournaled on pin 24 between the legs 21 for pivotal movement.

Note in Fig. 3 that latch 25 is provided with a transverse web 26perforated by a hole 27 for receiving the hooked end of a helicaltension spring 28. The other end of spring 28 is hooked in a hole 29 inthe bar 15 which spans the contact clips 10 transversely. Hence, spring28 urges latch 25 to pivot at all times in the direction of thelongitudinal axis of blade 5 toward the contact clips 10. To limit thepivotal movement of latch 25 toward contact clips 10, the latch isprovided with a stop in the form of a lateral projection 30 which abutsa margin of leg 21 in opposition to the force created by spring 28.Movement of latch. 25 against the tensile force of spring 28 is likewiselimited by a projection 31 as is evident from an inspection of Fig. 4.

Blade 5 is provided through its diameter with a latching pin 40 whichprojects from either side of the the blade periphery for positivelyengaging latch 25 when the blade is swung to closed circuit positionbetween contact clips 10. Latching pin 40 may be rigidly affixed inblade 5, as shown, or it may be journaled for rotation in the blade. Inthe latter construction it is necessary to retain the pin 40, againsttransverse movement with re spect to blade 5, by snap rings or othermeans (not shown) engaging pin 40 where it emerges from each side ofblade 5 immediately adjacent the periphery thereof. A bifurcatedhook-ring lever member 41 straddles the free end of blade 5 and ispivotally carried on the latching pin 40.

One end of the bifurcated lever member 41 is provided with an annularring 42 at its mid-section for receiving a hook stick (not shown) whenit is desired to actuate the latch 25 for the purpose of operating theswitch. The distance from latching pin 40 to the center of annular ring42 constitutes a lever arm which is long in comparison with itscorresponding resistance or prying arm, thereby enabling :an appreciablemechanical advantage to be developed when initially prying switch blade5 and actuating latch 25.

, At the other end of the bifurcated lever member 41 beyond latching pin4th will be seen two comparatively short arms 43 projecting away fromthe center of latching pin 40 at an angle relative to each other. Arms43 terminate in cam followers in the form of wing-like portions 44extending laterally therefrom, there being a total of four arms and fourcorresponding wing-like portions. When the switch blade 5 is swung tofully closed position, such as in Fig. 1, the wing portions 44 strikeagainst short cam surfaces 32, thereby acting as positive means forlimiting inward movement of the blade.

Cam surface 32 on latch 25 is a segment of a curve having radiiemanating from a point such as point 35 offset from the center of thelatch pivot pin 24 in a direction toward contact fingers ll). Hence, anyforce exerted normal to the cam surface 32 will have a component tendingto rotate the latch 25 about pin 24- in a clockwise direction, accordingto the law of moments, when viewed advantage and ice breaking ability.

in Fig. 3. This is an especially important feature because it assuresthat catch 33 will be urged into engagement with latching pin 40 even ifspring 28, which normally biases catch 33; in a clockwise direction, isweakened or entirely removed. Oby iously, if the radii of short camsurface 32 emanated from the center of pin 24, any force applied tosurface 32 would be transmitted radially to the pin affe'cting a thrustthereon instead of a rotational force thereabout.

Rocking movement of the bifurcated lever member 41 on pivot pin 48 islimited by a fixed cylindrical stop pin 45 which penetrates the diameterof blade parallel to pin '40 and is adapted for abutment with an arcuaterecess 46 defined by short arms 43.

In closing a switch of the type described herein the operatorwillfusually swing the blade 5 into latched position rapidly, butfirmly, by means of a hook stick engaged with ring 42. Then, inaccordance with the customary carefulness of such operators, the blade 5is tested for positive latching by attempting to open it throughexerting a pull directly on the blade adjacent its free end at aiplaceother than in ring 42. By reason of a small clearance existing betweenpin 40 and catch 33 when the blade 5 is swung to its full closedposition the operator, when testing, will effect a slight rotation ofblade 5 on its main pivot pin 4 which will take up this free playbetween the pin and catch. Conversely, the operator may, after testingthe blade for positive latching, push on it directly through the mediumof a hook stick to restore the aforementioned clearance, and urge blade5 as deeply as possible into contact fingers It When it is desired tofully release blade 5 from latch 25 prior to swinging the blade to opencircuit position or to take advantage ofthe double throw feature, it ismerely necessary to engage ring 42 with a hook stick (not shown) andpull thereon. As seen in the preceding para-graph either one of twoconditions may exist at this time; first, where there is clearancebetween pin 40 and catch 33 such as occurs when the switch blade 5 hasbeen tested and; second, where there is no clearance such as occurs whenthe blade by pulling directly on it has been tested but the clearancebetween pin 40 and catch 33 has not been restored.

Under the first condition, pivoting the lever member 41 will cause wings44 to bear reactively on cam surface 32 and pry the locking pin 4% intocontact with catch 33 without tending to swing the catch clear of thepin because latching pin 49 is in substantially the same vertical planeas pivot pin 24. Consequently, the entireforce transmitted through thehook stick is expended in breaking static seizure between fingers 19 andblade 5 and in fracturing ice which -may be present about the latchassembly. V p I Under the second condition, when there is no clearancebetween latching pin hi and catch 33, pivoting the lever memberdfl willcause earn followers in the form of wings 44 to pry the latch 25 andcatch 33 clear-of pin 40 without any swinging movement of blade 5occurring. However, under either condition, continued actuation of levermemher '41 will ultimately cause the short prying arms 43 to swing aboutlatching pin 4 in the manner shown in Fig.

.4, permitting wings 44 to exert a latch releasing force on cam surfaces32:: until catch 33 is cleared. Fig. 5 clearly shows that the sides onlatch 25 is such as to permit ongagement with pin 4t) but to allow freepassage therebetween of wings id when the switch is swung through thelatch into full open or closed circuit position.

It should be noted here that the ratio of the lever arms, extending fromthe center of pin 40 to ring 42, to the comparatively short prying arm43, extending from the same pin to-wings d4, results in obtainingoptimum mechanical in addition, it is to be especiaily noted that allreactive forces tending to pry the switch open are exerted between thebifurcated =rnem'ber 41 and latch 25, in contradistinction to the actionin prior art switches where a 'pivota'ble prying member frequentlyreacts against a fixed element, thus making the double action describedherein impossible in prior art switches.

Closing the switch blade 5 into electrical connection with the contactclips 10 simply involves swinging latch pin 40 into sliding contactrelation with beveled margin 3311 on latch until catches 33 thereofengage pin 40. Spring 28 will stretch and recoil to hold the latch 25firmly against latch pin 40, thereby preventing switch opening byvibratory forces incidental to heavy short .circuit currents and otherforces to which the switch may be subjected.

Note that beveled margin 33a constitutes a long inclined plane whichmaybe struck anywhere by latching pin when blade 5 is being pressed intothe latch. This feature enables the blade and latch to cooperateeffectively though there may be consideraable discrepancy in the spacingbetween insulators 1 and 1a. Furthermore, lateral misalignment of theblade 5 relative to latch 25 may also be appreciable because theoutwardly flared clips 10 act as a guide channel to properly positionthe blade within latch 25. Moreover, even if blade 5 were not guided byclips 10, the latch 25 would operate properly because it can toleratemisalignment to the extent that only apart of pin 40 projecting from oneside of blade 5 need engage with a catch 33 on the latch 25.

Although this specification and its accompanying drawings disclose anembodiment of the invention which facilitates convenient explanation ofits structure and mode of operation, other modifications of theinventionare intended to be within the purview of the disclosure and claims.

For example, it has been found advantageous in practice to make the freeend of blade 5, which carries the assembly constituting the stop pin andbifurcated lever member 41, an entirely separable part from blade 5.Such modification facilitates adapting the same size latch 20 and samesize lever member 41 to a switch blade 5 having greater or lesserdiameter than the one illustrated in the drawings. This is accomplishedby attaching the aforementioned assembly to the free end of blade 5 byany suitable coupling means such as a reducer or a cap which does notinterfere with the electrical engagement of blade 7 5 by fingers 10.

evident from the drawings that all parts are symmetrical inthemselvesand symmetrically arranged to facilitate double throw operation as well.Likewise, thelatch is shown embodied in a switch mountedhorizontallyoverhead, but those skilled in the art will immediately recognize thatthe latch will retain the switch blade in a selected position if theswitch were mounted vertically or in any intermediate position.

It is claimed:

1. In an electric switch, the combination of a hinge member, a contactmember and a switch blade mounted on said hinge member for swingingmovement relative to said contact member, a latch juxtaposed to saidcontact member, said latch having a cutaway portion definingintersecting catch and cam surfaces, said cam surface being intermediatesaid catch and the pivot axis of said latch,'-a spring interposedbetween said contact member .on each furcation and extending adjacentsaid cam surfaces on said latch when said switch is in latched position,

a stop pin transversely through said switch blade intermediate saidarms, and a hook stick ring integral with 'said bifurcated member,whereby rocking of said bifurcated member by means of said hook ringwill urge said latch clear of said latch pin and pry against said camsurfaces to urge said blade toward open circuit position.

2. In a double throw electric switch, the combination of a hinge member,contact members displaced from said hinge member and a switch blademounted on said hinge member for swinging movement relative to saidcontact members, a pivotable spring biased latch juxtaposed to eachcontact member respectively, each latch having a cutaway portiondefining intersecting catch and cam surfaces, said cam surface beingintermediate said catch and the pivot axis of said latch, a fixed latchpin transversely through said blade selectively engageable with one ofsaid catches in substantially the same plane as the latch pivot, abifurcated member straddling said blade at its free end and pivotallymounted on said latch pin, prying arms disposed on opposite sides ofsaid latch pin on each furcation thereof, a stop pin transverselythrough said switch blade intermediate said prying arms, a wing-likeportion integral with each arm and projecting laterally therefromadjacent said cam surfaces when said switch is in latched position, anda hook stick ring integral with said bifurcated member, whereby rockingof said bifurcated member by means of said hook ring will urge saidlatch clear of said latch pin and pry against said cam surfaces to urgesaid blade to open circuit position for selective engagement with eitherof said contact members.

3. In an electrical switch, the combination of, a base, a stationarycontact on said base, a hinge member spaced from said base, a switchblade pivotally mounted on said hinge member for engagement with saidstationary contact, a latch pin extending transversely through the freeend of said blade, a latch having a cutaway portion defining a catch andbeing pivotally mounted on said base about an axis parallel to the axisof said latch pin and resiliently urged from a first position whereinsaid latch pin is free of said catch portion to a second positionwherein said catch portion intereferes with said latch pin to preventopening of said switch blade, and a hook stick lever pivotally mountedintermediate its ends on said latch pin, one end of said leverconstituting an eye portion adapted to receive a hook stick and theother end thereof having a cam follower, said latch having a cam surfaceintersecting with said catch portion in the path of rotation of said camfollower and at an angle to the plane defined by the axis of the latchpin and the pivot axis of said latch, whereby rotation of said leverwill cause said cam follower to strike said cam surface with a forcewhich will tend to rotate said latch from said second to said firstposition and the reaction force on said camming surface will have acomponent along said axes tending to rotate said blade toward openposition.

4. A latch assembly for selectively engaging and re leasing the free endof a radially swingable switch blade, comprising, a latch pivotallymounted adjacent the circumferential path of said blade, said latchhaving a cutaway portion defining a catch projecting toward the pivotaxis of said blade and also defining dissimilar arcuate cam surfacesintermediate said catch and said latch pivot, one of said cam surfacesbeing generated by an arc having a center of curvature displaced fromthe pivot axis of said latch in a direction toward the pivot axis ofsaid blade, and said one cam surface being wholly displaced toward thepivot axis of said switch blade from a plane through the latch pivot andcatch, a transverse latch pin carried by said switch blade forengagement with said catch, a lever member pivotally mountedintermediate its ends on said latch pin, a hook stick ring integral withsaid lever at an end remote from the pivot axis of said blade, a camfollower integral with said lever at its other end, whereby swingingsaid cam follower into contact with said one cam surface will stop theswinging movement of said blade and rock said latch toward engagementwith the latch pin carried by said blade.

5. A latch assembly for selectively engaging and releasing the free endof a radially swingable switch blade, comprising, a latch pivotallymounted adjacent the path of circumferential movement of said blade,said latch having a cutaway portion defining a catch projecting towardthe pivot axis of said blade and also defining dissimilar arcuate camsurfaces intermediate said catch and said latch pivot, one of said camsurfaces being generated by an are having a center of curvaturedisplaced from the pivot axis of said latch in a direction toward thepivot axis of said blade and the other cam surface extending from saidcatch into intersection with said one cam surface, a transverse latchpin carried by said switch blade for engagement with said catch, a levermember pivotally mounted intermediate its ends on said latch pin, a hookstick ring integral with said lever member at an end remote from thepivot axis of said blade, a cam follower integral with said lever memberat its: other end and projecting adjacent the intersection of said camsurfaces, whereby pivoting said lever member by means of said hook stickring will cause said cam follower to rock said latch free of latch pinand pry against said one cam surface to initiate swinging of said blade.

References Cited in the file of this patent UNITED STATES PATENTS2,063,954 Ramsey Dec. 15, 1936 2,214,180 Reynolds Sept. 10, 19402,224,380 Crabbs et a1. Dec. 10, 1940

